Disclosed are methods and apparatuses for transmitting data using a random access procedure in a communication system. An operation method of a terminal in a communication system includes transmitting a first MsgA including an RA preamble #i and a payload to a base station; receiving, from the base station, a MsgB including information indicating that an RA preamble #k is reserved; and transmitting a second MsgA including the RA preamble #k and data to the base station in a preamble reservation period associated with the RA preamble #k.